Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus that subjects a substrate to gas-based processing.
Background Art
U.S. Pat. No. 6,921,556B2 discloses an exhaust duct through which a gas spent for film forming is discharged to the outside.
For example, on a film forming apparatus or an etcher, an exhaust duct is provided so as to surround a stage. A gas supplied onto the stage is radially diffused and taken in the exhaust duct. Preferably, the gas supplied onto the stage enters the exhaust duct radially and uniformly. In other words, for uniformly performing processing on a substrate on the stage with no location dependence, it is desirable that the gas flow rate at the edge of the stage is uniform.
However, the gas flow rate is increased in some location on the stage edge and is reduced in another location on the stage edge. Thus, there is a problem of the gas flow rate at the stage edge being not uniform. The seriousness of this problem is increased particularly when the pressure in the chamber is reduced to about 200 Pa while the amount of exhaust in the chamber is comparatively large.